This invention relates to a base film for three-dimensional conformability, and more particularly, to a film suitable as a base for transfer films or affixture films for three-dimensional conformability which combines excellent vacuum formability, heat resistance during injection molding and dimensional stability during printing of the film.
Application of three-dimensional printing onto the surface of a plastic article molded by a method such as injection molding has been carried out by transferring or affixing at the same time as molding. Of course, the film used in this transfer or affixture must have a three-dimensional shape which conforms to the shape of its article.
In the case of a transfer film, it is produced by first laminating, onto a plane base film, a releasable layer, a printing layer, and an adhesive layer in this order, and then subjecting the laminate to vacuum forming into a desired three-dimensional shape. Accordingly, it is necessary that the base film has good dimensional stability during printing, that its vacuum forming is easily carried out, and that the base film does not melt during injection molding.
Films which have heretofore been used as the film base are films of materials such as nylon, polyester, polypropylene, and polyvinyl chloride. While the nylon film has excellent vacuum formability and heat resistance, its tensile strength is weak and therefore its dimensional stability during printing is low. While the oriented polyester film has high dimensional stability during printing, its percent elongation is low and the vacuum formability at a temperature of about 100.degree. C. is inferior. While the rigid polyvinyl chloride film has good dimensional stability during printing and good vacuum formability, its heat resistance is inferior. For such reasons, there is no film which meets all of the requirements described above, although the realization of such a film has long been desired.